Continuous composite polyester filament yarn



10, 1964 w. H. JAMIESON 5 CONTINUOUS COMPQSITE POLYESTER FILAMENT YARNFiled Sept. 24, 1959 3 Sheets-Sheet 1 FIG. I

INVENTOR WILLIAM H. JAMIESON ATTORNEY Nov. 10, 1964 w. H. JAMIESON3,156,085

File d Sept. 24, 1959 3 Sheets-Sheet 2 FIG.30 FI6.3b FIG.4a FIG.4b

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1964 w. H. JAMIESON 3,156,085

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INVENTOR WILLIAM H. JAMIESON 3,156,085 CONTINUQUS COMPOSITE POLYESTERlFILAMENT YARN William H. Jamieson, Newark, Del., assignor to E. I.

du Pont de Nemours and Company, Wington, Del,

a corporation of Delaware Filed Sept. 24, 1959, Ser. No. 841,988 6Claims. ((31. 57140) This invention relates to composite polyester yarnsand the process for manufacturing said yarns. More particularly, thisinvention relates to composite polyester yarns which have a highlyuniform appearance in the form of dyed fabrics.

Synthetic linear condensation polyesters, and particularly the linearterephthalate polyesters, have attracted high commercial interest formany uses owing to their high tenacity, flexibility, crease resistance,low moisture absorption, and other valuable properties. Among suchpolyesters are polyethylene terephthalate and poly(phexahydroxylylenterephthalate). However, one difiiculty has been associated with thepolyesters in that the affinity of the polyester fibers for dyes changesmarkedly with variations in processing conditions. The sensitivity ofthe polyesters to varying conditions is such that even quite minorfluctuations in the process are sufiicient to cause noticeable changesin the dye aflinity of the fibers. In commercial production, it isfrequently observed that n'on-uniformities occur sporadically within asingle filament, or that one filament is continuously non-uniform wthrespect to the average. These non-uniformities are observed as light ordark streaks in dyed fabrics and are regarded as highly objectionable.

Attempts have been made to solve the problem of non uniform-ities invarious ways. In general, attention has been focused on greater controlof process variables such as polymer composition and molecuar weight,temperature during the spinning and orientation steps, and ten sionapplied during the various steps. However, due to the inherentdifiiculty of .the problem, these attempts have not met with completesuccess.

It is, therefore, an object of this invention to provide polyester yarnswhich have a uniform appearance in the form of dyed fabrics. Anotherobject is to provide such yarns by a process which is less sensitive tosmall fluctuations in process conditions than processes used heretofore.Other objects of this invention will appear here inafter.

Surprisingly, it has now been found that when filaments of differentcross section are spun together and forwarded as a single filamentbundle, the yarn so formed has a uniform appearance in the form of adyed fabric. When the dyed yarn is observed under magnification, it isseen that the individual filaments have varied shades of color. However,as seen :by the unaided eye, the overall appearance of the fabric isquite uniform. The yarn of which the fabric is made is also slightlymore bulky than conventional continuous filament yarn of homo geneouscross section, and this also contributes to the desirable appearance ofthe fabric.

In carrying out the process of the invention, a molten linearcondensation polyester is extruded through a plurality of spinneretorifices of different shapes. The polymer streams are then quenched andoriented, and the filaments so formed are forwarded as a single filamentbundle to a collecting device. The filaments assume essentially theshape of the orifice through which they are extruded. The forwardingspeeds may be selected within a wide range, forwarding speeds in excessof about 300 yards per minute usually being employed. It is generallydesired that the extruded filaments be'oriented to cause them to becometenacious. This may be done simply by winding the extruded filaments atvery high rates of speed, e.g., at about 3000 to 5200 yards per minute,as described by Hebeler in U.S. Patent 2,604,689. Alternatively, theextruded filaments may be wound up in a yarn bundle and then oriented bycold drawing the yarn up to about five times its original length in oneor more separate steps as disclosed by Whinfield and Dickson in U.S.Patent 2,465,319. Because the orientation of the yarn in the spinningstep increases with spinning speed, the draw ratio required to reach agiven level of of orientation in the yarn decreases as the spinningspeed increases.

In referring to the fiaments as having different cross sections, it ismeant that the cross sections should differ markedly. A convenientnumerical parameter relating to the shape of the cross sections is theshape factor, which is defined by the equation Shape Factor=P A where Pis the perimeter of the cross section and A is its area, measured in thesame units of length. Thus, a circle has a shape factor of 4 pi or 12.6;a square has a shape factor of 16; and a rectangle, having long sidesfour times the length of its short sides, has a shape factor of 25.

In accordance with the present invention, it has been found that atleast one species of filaments in the filament bundle should have ashape factor of at least about 18. Thus, round filaments may be combinedwith filaments having ribbon-shaped (elongated rectangular), Y- shaped,or cruciform cross sections having shape factors of at least about 18.

In the event that all of the filaments in the bundle have the samenumber of wel1-defined sides in cross section, i.e., have the samegeneral cross-sectional configuration, the shape :factors of at leasttwo species of filaments in the bundle should differ by a factor of atleast 1.4. The term sides is intended to include curved surfaces. Forinstance, two varieties of cruciform filaments having shape factorsdiffering by a factor of at least 1.4 may be combined in the samefilament bundle; or two varieties of ribbon-shaped cross sectionfilaments having shape factors differing by a factor of at least 1.4 maybe used.

All of the cross sections may have essentially the same shape factor,provided that the shape factor is at least about 18 and the filamentsdiffer markedly in cross-sectional shape. Preferably, in the lattercase, at least two species of the filaments in the bundle should havecross sections having different numbers of well-defined sides. Forexample, Y-shaped cross section yarn may be used with a cruciform crosssection yarn even though the two cross sections have the same shapefactor. Similarly, a cruciform cross section filament and aribbon-shaped cross section filament having the same shape factor may beused; or a cruciform cross section and a C-shaped cross section havingthe same shape factors may be used.

In accordance with the present invention, not more than about of any onespecies of the filaments in the filament bundle should have the sameshape factor and cross-sectional configuration.

In a preferred embodiment of the invention, three or more differentcross sections are used. In one particularly desirable embodiment, notmore than about 25% of each of several different species is utilized;Although each filament cross section need not be different, a variety ofcross sections in the filament bundle is conducive to better uniformity.Since the cross sections of the filaments are governed by the shape ofthe orifices in the spinneret, a variety of filament cross sections canbe obtained in each bundle simply by varying the orifice cross sectionsin the spinneret. i

If desired, the filaments may be of different denier as well as ofdifferent cross section. However, it is preferred that the filaments beof substantially the same denier throughout the filament bundle. Throughroutine experimentation, the hole size for each orifice cross sectionappropriate for substantially equivalent polymer flow rates through theorifices may be determined. However, a simpler method of achieving thisresult is the use of a metering plate containing capillary holes alignedwith the spinneret orifices. The diameter of the capillary holes in themetering plate are made sufficiently 1a; with respect to the spinneretorifices that most of the pressure drop across the metering plate andthe spinneret occurs within the metering plate. The denier of thefilaments is thereby controlled primarily by the metering plate; andwhen substantially uniform deniers are desired, the diameters of theorifices in the metering plate are made uniform.

The invention will be further illustrated by reference to theaccompanying drawings, in which:

FIGURE 1 is a schematic representation of suitable apparatus forspinning polyester filaments;

FIGURE 2 is a diagrammatic cross-sectional view of the portion of thespinnig head of FIGURE 1;

FIGURES 3a through 12a are bottom views of spinneret orifices of variouscross-sectional configuration; and

FIGURES 3b through 12b are cross sections of filaments spun from thecorresponding orifices of FIGURES 3a through 1241.

Referring now to FIGURE 1, the lower portion of a spinning head isrepresented by reference numeral 11. Molten polymer metered to cavity 12is extruded through orifices not illustrated forming filaments 13, 14,15, and 16. The filaments are drawn away from the orifice by means of apair of slightly axially skewed forwarding rolls 17 and 18, and aredelivered as a single yarn bundle to windup package 19. The yarn istraversed onto package 19 by means of a reciprocating traverse guide 20.

Referring to FIGURE 2, the spinning head includes a spinneret plate 21positioned in contact with a metering plate 22. Spinneret orifices 23,24, 25, and 26 are aligned with metering orifices 10. A cuppeddistributor plate 27, containing a plurality of holes 28, is locatedupstream from metering plate 22. The upstream face of distribution plate27 is in contact with screen 29. Retaining cap 30, which is threadedonto spinneret housing 31, secures the plates and screen in position.Pins 32 and 32 on spinneret plate 21 are recessed into holes in thebottom of metering plate 22 and serve to align the orifices in the twoplates. Gasket 33 provides a seal between screen 29, cupped distributionplate 27, and housing 31. The cavity 34 in housing 31 is filled with afiltering medium such as sand.

Both the metering orifices and spinning orifices 23, 24, 25, and 26 havecompound shapes. Orifices 10 consist of a capillary 35 and counterbore36. The spinneret orifices consist of jets 37 and counterbore 38. Thecounterbores and capillaries are circular in cross section; however, thejets may have various shapes as illustrated in FIGURES 3a through 120.The jets of spinneret orifices 23, 24, 25, and 26 are shown in FIGURES3a, 6a, 4a, and 8a, respectively. The counterbore crosssectional areasare several times larger than the corresponding capillary and jetcross-sectional areas.

FIGURE 3a illustrates a conventional orifice of round cross section, andFIGURE 3b illustrates the conventional, round cross section of afilament spun from this orifice.

FIGURE 4a illustrates a series of three round orifices spacedsufiiciently closely that the polymer streams extruded from the orificescoalesce at the spinneret face. The holes are arranged in a straightline to afford a variegated ribbon-like cross-sectional pattern in thecoalesced extruded filament, as shown in FIGURE 4b.

FIGURE 5a illustrates an orifice having the shape of a maltese cross.The cross section of the filament spun from the orifice is shown inFIGURE 51;.

FIGURE 6a illustrates an orifice of cruciform cross section, formed bythe intersection of two punched slots. The cross section of the fiberspun from the orifice is shown in FIGURE 6b.

FIGURE 7:: illustrates an orifice having the shape of a three-bladedpropeller. The cross section of the filament spun from the orifice isshown in FIGURE 7b.

FIGURE 8a illustrates a series of five punched holes of diamond-shapedcross section spaced sufficiently closely that the polymer streamsextruded from the orifices coalesce at the spinneret face. The holes arearranged in an arc to provide a variegated ribbon-like cross section inthe coalesced extruded filament, as shown in FIGURE 8b.

FIGURE 9a illustrates an orifice having the shape of a six-legged star.The cross section of a filament spun from the orifice is shown in FIGURE9b.

FIGURE 10a shows an orifice in the form of a twobladed propeller. FIGURE10b illustrates the cross section of a filament spun from the orifice.

FIGURE 11a illustrates an orifice having six round holes spaced inzigzag relationship which provides the filament of zigzag cross sectionshown in FIGURE 11b.

FIGURE 12a illustrates a four crosstie, ribbon-type orifice whichprovides a filament having a cross-section of the type shown in FIGURE12b.

In general, the variations in dye receptivity of filaments of differentcross section is observed most significantly when the filaments arecomposed of a linear condensation polyester. Preferably, in accordancewith the invention, a linear terephthalate polyester is employed. Bylinear terephthalate polyester is meant a linear polyester in which atleast about 75% of the recurring structural units are units of theformula wherein G represents a divalent organic radical containing from2 to 12 carbon atoms and is attached to the adjacent oxygen atoms bysaturated carbon atoms. Thus, the radical G may be of the form cH A CHwhere m is 0 or 1 and A represents an alkylene radical, a cycloalkyleneradical, a bis-alkylene ether radical, or other suitable organicradical. The linear terephthalate polyesters may be prepared by reactingterephthalic acid or an ester-forming derivative thereof with a glycol,G(OH) where --G- is a radical as defined above, to form the bis-glycolester of terephthalic acid, followed by polycondensation at elevatedtemperature and reduced pressure with elimination of excess glycol.Examples of suitable glycols include ethylene glycol, diethylene glycol,butylene glycol, decamethylene glycol, and cisortrans-bis-1,4-(hydroxymethyl) cyclohexane. Mixtures of such glycols maysuitably be used to form copolyesters, or small amounts, e.g., up toabout 15 mol percent, of a higher glycol may be used, such as apolyethylene glycol. Similarly, copolyesters may be formed by replacingup to about 25 mol percent of the terephthalic acid or derivativethereof with another dicarboxylic acid or ester-forming derivativethereof, such as adipic acid, dimethyl sebacate, isophthalic acid, orsodium 3,5-dicarbomethoxybenzenesulfonate.

Surprisingly, the novel yarns of the invention not only have a moreuniform appearance than conventional yarns of homogeneous cross sectionbut in fabric form they are also somewhat more bulky and have a morepleasing hand. This results in part from a differential response to heattreatment exhibited by linear terepbthalate polyester filaments ofvarious cross sections, in which the changes in length of the variousfilaments when heated differ by amounts ranging up to several percent.After the filaments are heated, the longer filaments are disposedoutwardly from the shorter filaments in the form of loops protrudingfrom the axis of the yarn bundle. The greater bulk of the yarn bundlealso results in part from the fact that filaments of different crosssection generally do not pack together in the yarn bundle as closely asfilaments of homogeneous cross section.

The following examples will serve to further illustrate the inventionand are not intended to be construed as limitative.

Example I A 5-inch stainless steel spinneret plate is preparedcontaining ten different orifice cross sections. Each of the orifices isprovided with a inch diameter counterbore section. The spinneretcontains a total of 34 orifices, seven round orifices and three of eachof the orifices having the configurations illustrated in FIGURES 4athrough 12a.

Polyethylene terephthalate having an intrinsic viscosity of 0.53 andcontaining 0.3% TiO is spun at 296 C. from the orifices described above,using a metering plate having 9-mil capillary sections above thespinneret plate. The filaments extruded from the spinneret are collectedas a single filament bundle. The filament bundle is wound up at a speedof 1200 yards per minute and it is found to have an as-spun denier of240. The spun yarn is oriented by passing it from a feed roll maintainedat 96 C. and operating at a peripheral speed of 150 yards per minute,thence to an unheated draw roll operated at a peripheral speed of 454yards per minute, after which the yarns are wound on a conventionalwindup. The drawn yarns are found to have a denier of 96.8, a tenacityof 2.5 grams per denier, and an elongation of 30.3%.

The drawn yarns are woven into a taffeta fabric containing 90 ends perinch in the warp and 76 ends per inch in the filling. The fabric is dyedfor four hours at 100 C. in a dye bath comprising 2% of l,4-diamino2,3-dichloroanthraquinone, based on the weight of the fabric. A controlfabric is prepared as just described except round filaments are utilizedin lieu of the filaments of different cross-sectional shapes. The dyedfabric is observed to be more uniform in appearance than the controlfabric prepared from the conventional, round cross section polyethyleneterephthalate yarn. The fabric prepared frorn the yarn containingfilaments of different cross section is also observed to be somewhatmore attractive in appearance and to have a somewhat softer hand thanthe control fabric.

Example 11 A 3-inch stainless steel spinneret is fabricated containingforty-four inch diameter counterbores. rom 22 of the counterbores 15-mildiameter round holes are drilled, while from the other 22 counterborescruciform orifices are prepared by punching two intersecting 4 x 34 milslots from each counterbore section. Polyethylene terephthalate havingan intrinsic viscosity of 0.53 and containing 0.2% Ti0 is spun at 295 C.from the spinneret, the filaments being wound up together as a singlebundle at 1200 yards per minute. The yarn is oriented as described inthe preceding example. The drawn yarn is found to have a denier of 61.0,a tenacity of 4.3 grams per denier, an elongation of 13.6%, and aninitial modulus of 114 grams per denier. Individual round and cruciformfilaments are teased out from the filament bundle and it is found thatthe round filaments have an average vibrational denier of 1.59 and anaverage shrinkage in 100 C. water of 9.8%, while the cruciform filamentsare found to have an average vibrational denier of 1.55 and an averageshrinkage of 9.12%.

The yarn is woven into a taffeta fabric containing 90 ends per inch inthe warp and 76 ends per inch in the filling. The fabric is dyed forfour hours at 100 C. in

6 a dye bath comprising 2% (based on the fabric weight) of a dye havingthe formula tional round cross section polyethylene terephthalate yarnprepared under the same conditions.

In addition to the procedures just described, the prod nets of thisinvention may also be prepared by combining filaments from differentspinnerets. They may be used in continuous filament or staple yarn form.

The novel yarns of this invention may be advantageously used in avariety of fabric constructions. They may be dyed either prior to orafter being knitted or woven into a fabric. They may be dyed usink knowndyes for polyester yarns.

As many widely different embodiments of this invention may be madewithout departing from the spirit and scope thereof, it is to beunderstood that this invention is not to be limited to the specificembodiments thereof except as defined in the appended claims.

I claim:

1. Linear polyester yarn having a uniform appearance in the form of dyedfabrics comprising a plurality of continuous filamentary structureshaving a uniform cross section along their length, said yarn consistingof at least two species of filamentary structures having differentcross-sectional shapes, the cross section of one of said species havinga shape factor of at least about 18, not more than about 75% of any oneof said species being present in said yarn, with the proviso that whenthe cross sections of said species have essentially the same number ofsides the shape factor of one of said species be at least 1.4 timesgreater than that of the other species.

2. The yarn of claim 1 wherein said polyester is polyethyleneterephthalate.

3. The yarn of claim 1 wherein the major portion of said filaments areround.

4. The yarn of claim 1 wherein at least three species of filaments arepresent in said yarn.

5. The yarn of claim 1 wherein all of said filaments have essentiallythe same denier.

6. A dyed fabric having a uniform appearance prepared from linearpolyester yarn comprised of a plurality of continuous filamentarystructures having a uniform cross section along their length, said yarnconsisting of at least two species of filamentary structures havingdifferent cross-sectional shapes, the cross section of one of saidspecies having a shape factor of at least about 18, not more than about75% of any one of said species being present in said yarn, with theproviso that when the cross sections of said species have essentialy thesame number of sides the shape factor of one of said species be at least1.4 times greater than that of the other species.

References Cited in the file of this patent UNITED STATES PATENTS1,964,659 Brumberger June 26, 1934 2,041,798 Taylor May 26, 19392,262,871 Whitehead Nov. 18, 1941 2,291,873 Brubaker Aug. 3, 19422,578,899 Pace Dec. 18, 1951 2,750,653 White June 19, 1956 2,804,645Wilfong Sept. 3, 1957 2,816,349 Pamm et a1 Dec. 17, 1957 (Gtherreferences on following page) 7 UNITED STATES PATENTS Smith Mar. 4, 1958Jarrett June 10, 1958 Sutor June 23, 1959 Groornbridge eta1 Sept. 22,1959 Holland June 7, 1960 Lehmicke July 19, 1960 3 Craig Nov. 15, 1960Groombridge et a1 Ian. 24, 1961 Waltz Apr. 18, 1961 Bottorf May 8, 1962FOREIGN PATENTS Great Britain Nov. 9, 1933

1. LINEAR POLYESTER YARN HAVING A UNIFORM APPEARANCE IN THE FORM OF DYEDFABRICS COMPRISING A PLURALITY OF CONTINUOUS FILAMENTARY STRUCTURESHAVING A UNIFORM CROSS SECTION ALONG THEIR LENGTH, SAID YARN CONSISTINGOF AT LEAST TWO SPECIES OF FILAMENTARY STRUCTURES HAVING DIFFERENTCROSS-SECTIONAL SHAPES, THE CROSS SECTION OF ONE OF SAID SPECIES HAVINGA SHAPE FACTOR OF AT LEAST ABOUT 18, NOT MORE THAN ABOUT 75% OF ANY ONEOF SAID SPECIES BEING PRESENT IN SAID YARN, WITH THE PROVISO THAT WHENTHE CROSS SECTIONS OF SAID SPECIES HAVE ESSENTIALLY THE SAME NUMBER OFSIDES THE SHAPE FACTOR OF ONE OF SAID SPECIES BE AT LEAST 1.4 TIMESGREATER THAN THAT OF THE OTHER SPECIES.